Lord of Light

On a colony planet settled long ago, the surviving crew of a lost generation ship have used mind-transfer and body-reincarnation technology to make themselves immortal, then recast themselves as the gods of the Hindu pantheon. They rule the planet's human population from a literal Heaven, suppressing technology to keep the masses dependent. One of the original crew, known as Sam, the Lord of Light, rejects this tyranny. Borrowing the teachings and role of the Buddha, he raises an army, allies with demons and renegade gods, and wages a long campaign to break the grip of heaven. Zelazny tells the story out of order, opening near the end and circling back through the war that brought Sam to that point.